Recently it has been shown that the two-sphere partition function of a gauged
linear sigma model of a Calabi-Yau manifold yields the exact quantum Kahler
potential of the Kahler moduli space of that manifold. Since four-dimensional
N=2 gauge theories can be engineered by non-compact Calabi-Yau threefolds, this
implies that it is possible to obtain exact gauge theory Kahler potentials from
two-sphere partition functions. In this paper, we demonstrate that the
Seiberg-Witten Kahler potential can indeed be obtained as a two-sphere
partition function. To be precise, we extract the quantum Kahler metric of 4D
N=2 SU(2) Super-Yang-Mills theory by taking the field theory limit of the
Kahler parameters of the O(-2,-2) bundle over P1 x P1. We expect this method of
computing the Kahler potential to generalize to other four-dimensional N=2
gauge theories that can be geometrically engineered by toric Calabi-Yau
threefolds.Comment: 12 pages + appendix; v2: minor corrections, reference adde